Slurry catalyst rejuvenation in-situ in slurry reactor

ABSTRACT

A process for rejuvenating reversibly deactivated catalyst particles in a three-phase slurry body of gas bubbles and catalyst particles in a slurry liquid, includes passing slurry from the top down to the bottom of the body through a slurry catalyst rejuvenating means. The slurry is sequentially passed through a first gas bubble reducing zone, a catalyst rejuvenating gas contacting zone, a second gas bubble reducing zone and then a downcomer transfer zone. The gas bubble reducing, contacting and at least a portion of transfer occur in slurry body. At least part of the means is in the slurry body.

BACKGROUND OF THE DISCLOSURE

[0001] 1. Field of the Invention

[0002] The invention relates to catalyst rejuvenation in a slurry. Moreparticularly the invention comprises rejuvenating catalyst particles ina three-phase slurry body, by sequentially passing slurry from the topdown to the bottom of the body through a first gas disengaging zone, arejuvenating gas contacting zone, a second gas disengaging zone and thena downcomer, and a means for achieving this. This is useful forrejuvenating a Fischer-Tropsch hydrocarbon synthesis catalyst in-situ ina slurry hydrocarbon synthesis reactor.

[0003] 2. Background of the Invention

[0004] Slurry hydrocarbon synthesis processes are well known anddocumented. In a slurry hydrocarbon synthesis process, synthesis gascomprising a mixture of H₂ and CO is bubbled up as feed gas through athree-phase, gas-liquid-solids slurry in a hydrocarbon synthesisreactor. The slurry liquid comprises hydrocarbon products of thesynthesis reaction, the solids comprise a suitable Fischer-Tropsch typehydrocarbon synthesis catalyst and the gas bubbles comprise the feed gasand gaseous products of the synthesis reaction. Synthesis gas made fromhydrocarbon feedstocks which contain nitrogen (i.e., natural gas) ornitrogen containing compounds (i.e., resids, coal, shale, coke, tarsands, etc.) invariably contains HCN and NH₃, either of whichdeactivates the catalyst. Some compounds formed in the slurry asby-products of the synthesis reaction, such as oxygenates, also causereversible deactivation. Catalyst deactivation by these species isreversible and catalytic activity is restored (the catalyst rejuvenated)by contacting the deactivated catalyst with a hydrogen rejuvenating gas.Thus, the activity of the hydrocarbon synthesis catalyst in the reactiveslurry may be intermittently or continuously rejuvenated by contactingthe slurry with hydrogen or a hydrogen containing gas, to form acatalyst rejuvenated slurry. This is disclosed, for example, in U.S.Pat. Nos. 5,260,239; 5,268,344; 5,817,702 and 5,811,468. In the '239 and'270 patents, rejuvenation takes place in an external vessel. In the'702 and '468 patents, slurry containing the rejuvenated catalyst ispassed up towards the top of the reactor, where the feed gasconcentration is low. It would be advantageous to be able to take theslurry to be rejuvenated from near the top of the reaction vessel,rejuvenate the catalyst inside, instead of in a vessel external of thereactor and then pass the rejuvenated slurry down near to the bottom ofthe vessel, to contact the incoming feed gas.

SUMMARY OF THE INVENTION

[0005] The invention relates to a process and means for slurry in-situcatalyst rejuvenation, in which slurry is passed from the top to thebottom of the slurry body in a reactor, through a rejuvenating zone andmeans located in the slurry body. The process rejuvenates the catalystin the slurry in, and not external to the reactor, thereby eliminatingthe need for an external rejuvenation vessel. The invention may bepracticed with any process employing a three-phase slurry in which thecatalyst reversibly deactivates and is rejuvenated with a suitablerejuvenating gas. An example of a particularly suitable process is aslurry Fischer-Tropsch hydrocarbon synthesis process, in which theslurry comprises a particulate catalyst and gas bubbles dispersed in ahydrocarbon slurry liquid. In a slurry hydrocarbon synthesis process,the feed gas concentration is greatest at the bottom of the slurry(slurry body) in the reactor. Therefore, it is advantageous to removethe deactivated catalyst from near to the top of the slurry body wherethe concentration of the feed gas is lowest and pass the rejuvenatedcatalyst down to the bottom portion of the reactor. By slurry body ismeant the body of three-phase slurry in reactor. By top and bottom ofthe slurry body, is respectively meant above and below the middle of theslurry body, and preferably as near to the top and bottom as possible.

[0006] Briefly, the process comprises rejuvenating reversiblydeactivated catalyst particles in a three-phase slurry body, bysequentially passing slurry from the top down to the bottom of the bodythrough a first gas disengaging zone, a rejuvenating gas contactingzone, a second gas disengaging zone and then a downcomer or transferzone down, all of which occurs within the slurry body. Further, exceptfor the first gas disengaging zone and the bottom exit of the downcomertransfer zone, the slurry being processed according to the invention isisolated from direct contact with the surrounding slurry body. Havingthe rejuvenation zone and the second gas disengaging and downcomer zonesisolated from direct contact with the surrounding slurry body, enablesthe slurry to be rejuvenated by the process of the invention while thereactor is either off-line or on-line producing products. Therejuvenation process may be conducted continuously or intermittently inthe reactor. At least a portion, but not necessarily all, of the gasbubbles in the slurry are removed in the gas disengaging zones. Thefirst gas disengaging zone removes gas bubbles from the slurry as itpasses through the zone, to produces a gas reduced slurry that passesinto the rejuvenating zone, into which a rejuvenating gas is passed andcontacts the catalyst particles in the gas reduced slurry. Thisrejuvenates the catalyst in the slurry and forms a rejuvenated slurrycontaining bubbles of rejuvenating gas, which is then passed through asecond gas disengaging zone, to remove bubbles of rejuvenating gas andform a gas reduced and rejuvenated slurry, which is passed down to thebottom of the slurry body. By rejuvenated slurry is meant slurry inwhich the catalyst particles have been at least partially rejuvenated.By removing bubbles is meant that at least a portion of the gas bubblesis removed, as is explained below. Removing gas bubbles from the slurryincreases its density, compared to the lower density of the higher gascontent surrounding slurry body and slurry being rejuvenated in therejuvenating zone. This density difference enables the rejuvenationprocess to be conducted entirely by gravity driven hydraulics. Thus,there is no need for slurry pumps.

[0007] Means useful for rejuvenating a reversibly deactivated catalystaccording to the process of the invention conducting the process of theinvention may comprise a simple closed vessel at least partiallyimmersed in the slurry body, having a slurry entrance and exit, andmeans for injecting rejuvenating gas up into its interior. The entranceand exits are in direct fluid communication with the first and secondgas disengaging means, each of which may comprise an upward opening cupor conduit that permits gas bubbles to rise up and out of the slurrypassing through and which respectively feeds the gas-reduced slurry intothe interior of the vessel and into a downcomer. The downcomer may be asimple, vertical pipe or conduit open at its top and bottom, part ofwhich is immersed in the slurry body and feeds the rejuvenated andgas-reduced slurry down into the bottom of the surrounding slurry andwith its top extending up and out the top of the slurry body, to permitthe disengaged rejuvenating gas bubbles leave the slurry, before or asit passes down the conduit.

[0008] The invention briefly comprises a process for rejuvenatingreversibly deactivated catalyst particles in a three-phase slurry,wherein slurry from a slurry body is sequentially passed from the topdown to the bottom of the body through a first gas bubble reducing zone,a rejuvenating gas contacting zone in which a catalyst rejuvenating gascontacts the catalyst which is at least partially rejuvenated, a secondgas bubble reducing zone and then a downcomer or transfer zone, whereinthe gas bubble reducing and contacting occur within the slurry body,wherein at least a portion of the transfer zone is in the body andwherein the slurry comprises gas bubbles and solid catalyst particles ina slurry liquid. The bubble reducing zones, the rejuvenating gascontacting zone and at least a portion of the downcomer transfer zoneare part of a single catalyst rejuvenating means at least partiallyimmersed in the slurry body. In the embodiment in which the singlerejuvenating means is immersed in a slurry in a slurry reactor, then theall of the downcomer transfer zone will also be immersed in the slurrybody in the reactor. In greater detail the invention comprises a processfor rejuvenating a reversibly deactivated catalyst in a three phaseslurry body in a vessel, wherein the slurry comprises a slurry liquid inwhich is dispersed gas bubbles and particles of the catalyst, theprocess comprising (i) passing slurry from the upper portion of theslurry body through a first gas bubble reducing zone, to disengage andremove at least a portion of the bubbles and form a gas bubble reducedslurry, (ii) passing the gas bubble reduced slurry into a rejuvenatingzone, (iii) passing a rejuvenating gas into the rejuvenating zone, inwhich it contacts the catalyst particles in the slurry and reacts withthem to rejuvenate at least a portion and form a rejuvenated slurrycontaining gas bubbles, (iv) passing the rejuvenated slurry through asecond gas bubble reducing zone to remove gas bubbles and form a gasbubble reduced and rejuvenated slurry and (iv) passing the gas bubblereduced and rejuvenated slurry into a downcomer slurry transfer zone, inwhich the gas bubble reduced and rejuvenated slurry passes down and intothe lower portion of the slurry body, and wherein the gas bubblereducing zones, the rejuvenating zone and at least a portion of thedowncomer slurry transfer zone are located in the slurry body. In thespecific case of a slurry Fischer-Tropsch hydrocarbon synthesis process,the rejuvenation gas will be hydrogen or a hydrogen-containing gas.

[0009] In an embodiment with specific regard to a slurry hydrocarbonsynthesis process, the invention comprises the steps of:

[0010] (a) contacting a synthesis gas comprising a mixture of H₂ and COwith a particulate hydrocarbon synthesis catalyst in the presence ofcatalyst deactivating species, in a slurry body comprising the catalystand gas bubbles in a hydrocarbon slurry liquid, in which the H₂ and COreact under reaction conditions effective to form hydrocarbons from saidsynthesis gas, at least a portion of which are liquid at the reactionconditions and form the slurry liquid, and wherein the deactivatingspecies reversibly deactivate the catalyst;

[0011] (b) passing slurry from the upper portion of the slurry bodythrough a first gas bubble reducing zone, to remove at least a portionof the gas bubbles from the slurry and form a gas bubble reduced slurry;

[0012] (c) passing the gas bubble reduced slurry into a catalystrejuvenation zone;

[0013] (d) passing a catalyst rejuvenating gas comprising hydrogen intothe rejuvenation zone in which it contacts and reacts with the catalystparticles in the slurry, to rejuvenate and at least partially restorethe activity of the catalyst to form (i) a rejuvenating offgas and (ii)a rejuvenated catalyst slurry containing bubbles comprising offgas andunreacted rejuvenating gas;

[0014] (e) passing the rejuvenated catalyst slurry into a second gasbubble removing zone to remove at least a portion of the gas bubblesfrom the rejuvenated slurry to form a gas reduced and rejuvenatedcatalyst slurry, and

[0015] (f) passing the gas reduced and rejuvenated slurry into adowncomer slurry transfer zone in which it is passed down and into thebottom portion of said slurry body and wherein the gas bubble reducingzones, the rejuvenating zone and at least a portion of the downcomerslurry transfer zone are located in the slurry body.

[0016] The slurry reactor may be operating during rejuvenation or it maybe taken off-line and batch rejuvenated. The rejuvenation steps (b)through (f) may be conducted either continuously or on a cyclical basis.When rejuvenation occurs while the hydrocarbon synthesis reactor ison-line and producing hydrocarbon liquids, a portion of these liquids iseither continuously or intermittently withdrawn from the reactor assynthesized hydrocarbon product. In the context of the invention, theterm “catalyst deactivating species” is meant to include species whichreversibly deactivate the catalyst and wherein the catalyst activity isrestored (the catalyst rejuvenated) by contact with a rejuvenating gasin-situ in the slurry liquid. Hydrogen or a hydrogen containing gas isuseful for such rejuvenation in a hydrocarbon synthesis process, as hasbeen demonstrated in the prior art. Finally, while HCN, NH₃ and certaintypes of oxygenates will deactivate a hydrocarbon synthesis catalyst,the invention is not intended to be limited to use only with ahydrocarbon synthesis process or a hydrogen rejuvenating gas, but isuseful with any slurry reaction, catalyst and species which reversiblydeactivate the catalyst and wherein the catalyst activity can berestored with an appropriate rejuvenating gas.

BRIEF DESCRIPTION OF DRAWINGS

[0017]FIG. 1 is a schematic cross-section of a rejuvenation means of theinvention in a slurry hydrocarbon synthesis reactor.

[0018]FIG. 2 is an enlarged schematic cross-section of the rejuvenationmeans of the invention shown in FIG. 1.

[0019]FIG. 3 is a plan top view of the rejuvenation vessel shown inFIGS. 1 and 2.

[0020]FIG. 4 illustrates a cross-sectional side view of anotherembodiment of part of the means shown in FIG. 2.

[0021]FIG. 5 is a brief plan top view of a detail of the means in FIGS.1 and 2.

DETAILED DESCRIPTION

[0022] The invention will be illustrated in more detail, with specificregard to an embodiment in which it is employed to rejuvenate thecatalyst particles in a slurry Fischer-Tropsch hydrocarbon synthesisreactor, that is producing hydrocarbons from a synthesis gas feed. As isknown, in a slurry Fischer-Tropsch hydrocarbon synthesis process, asynthesis gas feed comprising a mixture of H₂ and CO is bubbled up intoa slurry in which the H₂ and CO react in the presence of a suitablecatalyst, under reaction conditions effective to form hydrocarbons, andpreferably liquid hydrocarbons. Slurry hydrocarbon synthesis processconditions vary somewhat depending on the catalyst and desired products.Typical conditions effective to form hydrocarbons comprising mostly C₅₊paraffins, (e.g., C₅₊-C₂₀₀) and preferably C₁₀₊ paraffins, in a slurryhydrocarbon synthesis process employing a catalyst comprising asupported cobalt component include, for example, temperatures, pressuresand hourly gas space velocities in the range of from about 320-600° F.,80-600 psi and 100-40,000 V/hr/V, expressed as standard volumes of thegaseous CO and H₂ mixture (60° F., 1 atm) per hour per volume ofcatalyst, respectively. A catalyst comprising a catalytic cobaltcomponent is known to produce mostly hydrocarbons that are liquid andsolid at room temperature, but liquid at the reaction conditions. Whilethe mole ratio of the hydrogen to the carbon monoxide in the gas maybroadly range from about 0.5 to 4, the stoichiometric consumption moleratio for a slurry Fischer-Tropsch hydrocarbon synthesis reaction istypically about 2.1 in a slurry hydrocarbon synthesis process conductedunder non-shifting conditions. A synthesis gas having other than astoichiometric H₂ to CO mole ratio may also be used, as is known, adiscussion of which is beyond the scope of the present invention.Synthesis gas may be formed by various means from coke, coal, bitumen,hydrocarbons and other hydrocarbonaceous materials. U.S. Pat. No.5,993,138 gives a good review of various processes used to producesynthesis gas and their relative merits. A feed comprising methane, asin natural gas, is preferred for convenience, cleanliness and because itdoesn't leave large quantities of ash to be handled and disposed of.Irrespective of the hydrocarbonaceous source used to produce thesynthesis gas, they all typically contain nitrogen or nitrogencontaining compounds that result in the presence NH3 and HCN in thesynthesis gas. These will deactivate a Fischer-Tropsch hydrocarbonsynthesis catalyst, particularly one comprising Co as the catalyticmetal. Oxygenates are formed during hydrocarbon synthesis and can alsodeactivate the catalyst. Further, water can oxidize the surface of thecatalytic metal component. It has been found that deactivation by thesespecies is reversible and the catalyst can be rejuvenated by contactingit with hydrogen. This restoration of the catalytic activity of areversibly deactivated catalyst is referred to as catalyst rejuvenation.However, while preferred and possible, complete restoration of thecatalytic activity for all of the catalyst particles in the slurrypassing through the rejuvenation means may not always be achieved. It'sfor this reason the expression “at least partially rejuvenates thecatalyst” and the like, are used herein. The rejuvenation process alsoproduces a rejuvenation product gas, which is referred to herein as arejuvenation offgas, and this offgas contains some of the same catalystdeactivating species present in the synthesis gas that resulted in thecatalyst deactivation in the first place (e.g., NH₃ and HCN). Thereforeit is also desirable to remove this offgas from the rejuvenated slurry,before it passes back into the slurry body in the hydrocarbon synthesisreactor, to avoid recontaminating the slurry with the catalystdeactivating species removed by the rejuvenation. The rejuvenation willtypically occur at the synthesis conditions when the process of theinvention takes place in the synthesis reactor or reactor vessel, asopposed to a vessel exterior of the reactor. While it may be conductedin an exterior vessel, it is preferred that it be conducted in thesynthesis reactor itself.

[0023] During rejuvenation, the presence of CO in the rejuvenation zonehinders catalyst rejuvenation until the CO is consumed. Thus, removingat least a portion of the gas bubbles which contain unreacted synthesisgas from the slurry before it is passed into the rejuvenation zone,substantially reduces the amount of CO present during rejuvenation. Thisreduces the amount of rejuvenation hydrogen needed and also results in agreater degree of rejuvenation. Further, the hydrogen or hydrogencontaining rejuvenation gas passed into the rejuvenation zone raises theH₂ to CO mole ratio to greater than the stoichiometric. This results inconversion of the CO in the rejuvenation zone primarily to methane, andalso tends to promote hydrogenolysis and cracking of the hydrocarbonliquid to lighter products (such as methane). For these reasons, it isbeneficial to remove as much of the gas bubbles as is possible from theslurry before it is rejuvenated. The invention will be furtherunderstood with respect to the embodiments illustrated in the Figures.

[0024]FIG. 1 shows a slurry hydrocarbon synthesis reactor 10, brieflyillustrated in schematic cross-section, as comprising a cylindricalvessel 12 containing a rejuvenation means of the invention 14 within. Afeed gas line 16 feeds the synthesis gas feed up into the bottom of thereactor via a gas distribution grid or tray briefly illustrated asdashed line 18. Grid 18 is located over plenum space 20 and at thebottom of the three-phase slurry body 22 in the reactor. Except for gasdistributors arrayed across its surface and extending through it, grid18 is impervious to gas and liquids. Unreacted synthesis gas and gasproducts of the hydrocarbon synthesis reaction rise up out of theslurry, collect in gas space 24 at the top of the vessel and are removedby a gas product line 26. The slurry comprises a hydrocarbon liquid inwhich catalyst particles and gas bubbles are dispersed. The circles anddots respectively represent the gas bubbles and solid catalystparticles. The slurry hydrocarbon liquid comprises hydrocarbon productsof the synthesis reaction that are liquid at the reaction conditions.The gas bubbles comprise the uprising synthesis gas, along with gasproducts of the synthesis reaction, a significant amount of whichcomprises steam or water vapor. A hydrocarbon liquid product withdrawalmeans 28, such as a filter, is located within the slurry body 22 forwithdrawing the liquid hydrocarbon products from the reactor, via line30. Catalyst rejuvenation means 14, shown enlarged in FIG. 2, comprisesa cylindrical vessel 32, having conical upper 34 and lower 36 portions,joined by a vertical cylindrical center wall portion 38. If desired ornecessary due to space limitations in the reactor, part of the upperconical portion 34 of vessel 32 may extend up out of the slurry. Adowncomer 40, having respective upper and lower portions 42 and 44,comprises a hollow, vertical conduit, such as a pipe, in fluidcommunication with the interior of the rejuvenation vessel 32, viaconnecting fluid conduit 52. The lower portion 44 of the downcomercomprises the slurry transfer means, for passing rejuvenated slurry thathas been reduced in gas bubbles down to the bottom portion of the slurrybody. Portion 44 is wholly immersed in the slurry body, as shown.However, if the rejuvenation means 14 is in a vessel external of vessel12, then at least a portion of the rejuvenated slurry transfer meanswill be located in the slurry body. A simple conical-shaped baffle 46,located just below the rejuvenated slurry exit at the bottom of thedowncomer, prevents the uprising synthesis gas bubbles from entering upinto the downcomer. If desired or necessary, an optional rejuvenationgas line 48 may be used to inject small amounts of a hydrogen-containingrejuvenation gas up into the downcomer, to maintain catalytic activityof the rejuvenated catalyst in the downflowing rejuvenated slurry. Alsoassociated with the rejuvenating means 14 is a gas line 54, for passinga rejuvenating gas into the bottom of the interior of the vessel 32, andup through a gas distribution means 56, indicated by the dashed line.First and second gas bubble disengaging zones are respectively shown as55 and 62. Zone 62 comprises the interior of the conduit 52 connectingthe vessel 32 to the downcomer 40. A simple baffle plate 58, shownextending transversely across the interior of rejuvenation vessel 32,divides most of the interior of the vessel into two different fluid flowzones. This prevents the incoming, gas-bubble reduced slurry entering 32from the slurry body, from flowing transversely across the interior ofvessel 32 and then out and down through the downcomer, without havinghad sufficient contact with the hydrogen to rejuvenate the catalystparticles in the slurry. Thus, the three-phase slurry from the slurrybody 22 in reactor 10 disengages gas bubbles in zone 55, to form aslurry reduced in gas bubbles. This increases the density of thegas-reduced slurry, which then flows down, via slurry conduit 66, intothe interior of the rejuvenating vessel 32 and forms a rejuvenatingslurry body 60. The slurry flow through the vessel 32, due to thepresence of the flow-dividing baffle 58, is shown by the arrows. Theuprising rejuvenating gas, in this case bubbles of hydrogen or asuitable hydrogen-containing gas indicated by the circles, contacts thedeactivated catalyst particles in the slurry as it flows down, acrossand up through the interior of the vessel, and then out through conduit52 into downcomer 40. As the slurry flows through the conduit 52, gasbubbles comprising the rejuvenating gas and gaseous rejuvenationproducts rise up and out of the rejuvenated slurry. This increases thedensity of the slurry to greater than that of the surrounding slurrybody, enabling the now gas-reduced and rejuvenated slurry to flow intodowncomer 40, and down through lower portion 44, due to the densitydifference. As the hydrogen in the rejuvenating gas contacts thecatalyst particles in the slurry flowing through the rejuvenating vesselit reacts with them, thereby rejuvenating them and restoring at least aportion of their catalytic activity. This forms a rejuvenating offgascomprising unreacted hydrogen and gaseous products of the rejuvenationreaction. As shown in FIGS. 1 and 2, this offgas rises up into the upperportion 42 of the downcomer conduit, which carries it out of thesynthesis reactor as shown in FIG. 1.

[0025] Returning to vessel 32, FIGS. 1, 2 and 3 show the first gasdisengaging zone 55 as comprising an arcuate cavity in the shape of asector of an annulus, in fluid communication with the surroundingslurry. This is formed by an inner wall 68 extending vertically downfrom the conical top 34 of vessel 32 to form part of conduit 66. Wall 68is curved, with its perimeter parallel to that of the vertical outerwall 38 of the vessel. A downwardly sloping bottom wall 70 extendsradially inward from the upper edge 72 of vertical wall 38, andterminates at its bottom in a curved vertical wall 74 which, togetherwith wall 68, forms slurry conduit 66. As shown in FIGS. 1, 2 and 4,wall 74 extends vertically downward from the bottom edge of 70. Theperimeter of both 70 and 74 are also parallel to that of 38. Wall 70slopes down at an angle greater than the angle of friction (angle ofrepose) of the catalyst particles in the slurry, to prevent build-up ofslurry particles in the first gas disengaging zone 55. FIG. 4 is apartial cross-sectional schematic view illustrating another embodimentof the first gas disengaging zone, section A. In this embodiment,instead of forming edge 72, a portion 39, of vertical wall 38 of vessel32 extends vertically up as high as the intersection of 68 and 34. Thiswall extension provides a larger and deeper gas bubble disengaging zone.Thus, providing the extending vertical wall extension 39 provides alarger quiescent zone, in which the slurry within has more time todisengage gas bubbles, and with substantially less disturbance from thesurrounding slurry 22. This is a preferred embodiment over that shown inFIGS. 1 and 2. FIG. 5 is a top plan view of a partial cross-section ofslurry conduit 52, illustrating a detail of one embodiment of the shapeof the conduit, which also functions in this embodiment as the secondgas bubble disengaging zone 62. Referring to both FIGS. 2 and 5, in thisembodiment the upper and lower walls 76 and 78 of the conduit 52, arerespectively sloped upward and downward, as they extend radially outwardfrom the vessel wall 38. The downward slope of 78 enables theintersection 80, of the upper portion of 78 with the vertical, outerwall of vessel 32, to act as a weir. It also increases the size of gasdisengaging zone 62, as well as the gas and slurry entrance area intodowncomer 40. The side walls 82 and 84 provide a fluid opening todowncomer 40 substantially larger than if they were parallel andlaterally spaced apart the same distance as the inside diameter of 40.This all maximizes gas disengagement in 62 and minimizes slurry flowreduction into 40 by the outflowing rejuvenation offgas.

[0026] It is understood that various other embodiments and modificationsin the practice of the invention will be apparent to, and can be readilymade by, those skilled in the art without departing from the scope andspirit of the invention described above. Accordingly, it is not intendedthat the scope of the claims appended hereto be limited to the exactdescription set forth above, but rather that the claims be construed asencompassing all of the features of patentable novelty which reside inthe present invention, including all the features and embodiments whichwould be treated as equivalents thereof by those skilled in the art towhich the invention pertains.

What is claimed is:
 1. A process for rejuvenating reversibly deactivatedcatalyst particles in a three-phase slurry body comprises sequentiallypassing slurry from the top down to the bottom of said body through afirst gas bubble reducing zone, a rejuvenating gas contacting zone inwhich a catalyst rejuvenating gas contacts said catalyst which is atleast partially rejuvenated, a second gas bubble reducing zone and thena downcomer or transfer zone, wherein said gas bubble reducing andcontacting occur within said body, wherein at least a portion of saidtransfer zone is in said body and wherein said slurry comprises gasbubbles and solid catalyst particles in a slurry liquid.
 2. A processaccording to claim 1 wherein said reducing and contacting zones are partof a single catalyst rejuvenating means at least partially immersed insaid slurry body.
 3. A process for rejuvenating a reversibly deactivatedcatalyst in a three phase slurry body in a vessel, wherein said slurrycomprises a slurry liquid in which is dispersed gas bubbles andparticles of said catalyst, said process comprising (i) passing slurryfrom the upper portion of said slurry body through a first gas bubblereducing zone, to disengage and remove at least a portion of saidbubbles and form a gas bubble reduced slurry, (ii) passing said gasbubble reduced slurry into a rejuvenating zone, (iii) passing arejuvenating gas into said rejuvenating zone, in which it contacts saidcatalyst particles in said slurry and reacts with them to rejuvenate atleast a portion and form a rejuvenated slurry containing gas bubbles,(iv) passing said rejuvenated slurry through a second gas bubblereducing zone to remove gas bubbles and form a gas bubble reduced andrejuvenated slurry and (iv) passing said gas bubble reduced andrejuvenated slurry into a downcomer slurry transfer zone, in which saidgas bubble reduced and rejuvenated slurry passes down and into the lowerportion of said slurry body, and wherein said gas bubble reducing zones,said rejuvenating zone and at least a portion of said downcomer slurrytransfer zone are located in said slurry body.
 4. A process according toclaim 3 wherein said gas bubbles in said rejuvenated slurry formed insaid rejuvenating zone comprises at least one of (i) unreactedrejuvenating gas and (ii) gaseous products of said rejuvenation.
 5. Aprocess according to claim 4 wherein said reducing and contacting zonesare part of a single catalyst rejuvenating means at least partiallyimmersed in said slurry body.
 6. A process according to claim 5 whereinsaid vessel comprises a reactor.
 7. A process according to claim 5wherein said slurry comprises a hydrocarbon liquid containing gasbubbles and catalyst particles.
 8. A process according to claim 7wherein said reactor comprises a hydrocarbon synthesis reactor.
 9. Aprocess according to claim 8 wherein said hydrocarbon liquid comprisessynthesized hydrocarbons that at liquid at the reaction conditions insaid reactor.
 10. A slurry hydrocarbon synthesis process comprises thesteps of: (a) contacting a synthesis gas comprising a mixture of H₂ andCO with a particulate hydrocarbon synthesis catalyst in the presence ofcatalyst deactivating species, in a slurry body comprising said catalystand gas bubbles in a hydrocarbon slurry liquid, in which said H₂ and COreact under reaction conditions effective to form hydrocarbons from saidsynthesis gas, at least a portion of which are liquid at the reactionconditions and form said slurry liquid, and wherein said deactivatingspecies reversibly deactivate said catalyst; (b) passing slurry from theupper portion of said slurry body through a first gas bubble reducingzone, to remove at least a portion of said gas bubbles from said slurryand form a gas bubble reduced slurry; (c) passing said gas bubblereduced slurry into a catalyst rejuvenation zone; (d) passing a catalystrejuvenating gas comprising hydrogen into said rejuvenation zone inwhich it contacts and reacts with said catalyst particles in saidslurry, to rejuvenate and at least partially restore the activity ofsaid catalyst to form (i) a rejuvenating offgas and (ii) a rejuvenatedcatalyst slurry containing bubbles comprising said offgas and unreactedrejuvenating gas; (e) passing said rejuvenated catalyst slurry into asecond gas bubble removing zone to remove at least a portion of said gasbubbles from said rejuvenated slurry to form a gas reduced andrejuvenated catalyst slurry, and (f) passing said gas reduced andrejuvenated slurry into a downcomer slurry transfer zone in which it ispassed down and into the bottom portion of said slurry body and whereinsaid gas bubble reducing zones, said rejuvenating zone and at least aportion of said downcomer slurry transfer zone are located in saidslurry body.
 11. A process according to claim 10 wherein said catalystcomprises a Fischer-Tropsch hydrocarbon synthesis catalyst.
 12. Aprocess according to claim 11 wherein said catalyst comprises acomposite of at least one Group VIII catalytic metal component and asupport component.
 13. A process according to claim 12 wherein saidreducing and contacting zones and at least a portion of said transferzone are part of a single catalyst rejuvenating means at least partiallyimmersed in said slurry body.
 14. A process according to claim 13wherein said slurry body is located in a slurry hydrocarbon synthesisreactor.
 15. A process according to claim 14 wherein all of saidtransfer zone is located is said slurry body.
 16. A means forrejuvenating a reversibly deactivated catalyst in a three phase slurrybody comprising deactivated catalyst particles and gas bubbles in aslurry liquid comprises (a) a hollow rejuvenation vessel at leastpartially immersed in said slurry body and having a rejuvenation zonewithin its interior and means for injecting rejuvenating gas up intosaid zone, (b) a slurry entrance comprising a first gas slurry gasbubble reducing zone, (c) a slurry exit comprising a second slurry gasbubble reducing zone, and (d) a slurry downcomer transfer zone, whereinsaid entrance and exits are respectively in fluid communication withsaid slurry body and downcomer.
 17. A slurry hydrocarbon synthesisreactor containing a three phase slurry within which comprises catalystparticles and gas bubbles in a slurry liquid, also contains within meansfor rejuvenating said catalyst particles, wherein said rejuvenatingmeans comprises comprises (a) a hollow rejuvenation vessel at leastpartially immersed in said slurry body and having a rejuvenation zonewithin its interior and means for injecting rejuvenating gas up intosaid zone, (b) a slurry entrance comprising a first gas slurry gasbubble reducing zone, (c) a slurry exit comprising a second slurry gasbubble reducing zone, and (d) a slurry downcomer, wherein said entranceand exits are respectively in fluid communication with said slurry bodyand downcomer. and wherein said rejuvenation zone, slurry entrance andexit and said downcomer are all immersed in said slurry body in saidreactor.